Wireless Terminal Apparatus and Wireless Base Station Apparatus

ABSTRACT

Both a wireless terminal apparatus and wireless base station apparatus are provided that can, in an operation of encoding the control signals of the upstream link transmitted from the multiple terminal stations while encoding with regard to each of the terminal stations, increase a number of the terminal stations to which different codes are respectively assigned. A wireless terminal apparatus includes: an encoding information receiving portion receiving encoding information which is used at the wireless terminal apparatus from the base station; a phase-shifting unit which conducts a phase-shifting operation on a predetermined first code based on the encoding information; a code selection unit which, based on the received encoding information, selects a second code from multiple codes orthogonally crossing each other; and a control signal encoding portion which conducts an encoding operation on the control signal that is going to be transmitted to the base station by using both the first code on which the phase-shifting operation has been conducted and the second code.

TECHNICAL FIELD

The present invention relates to a wireless terminal apparatus and awireless base station apparatus.

Priority is claimed on Japanese Patent Application No. 2006-296910,filed Oct. 31, 2006, the content of which is incorporated herein byreference.

BACKGROUND ART

In recent years, a standardization project “3GPP: 3rd GenerationPartnership Project” has been discussing a standard regulation of athird generation (3G) mobile communication system. One of topics whichhas been discussed is a control signal transmission method of anupstream link (link in a direction from a terminal station to a basestation).

For example, Non-Patent Document 1 proposes a method of encoding bothACK/NACK signals transmitted from multiple terminal stations and CQI(Channel Quality Indicator) signals at the upstream link with regard toeach of the terminal stations. ACK/NACK signals are response signals of1 bit for confirmation of transmission, ACK signal has a bit “1” usedwhen responding positively, and NACK signal is a bit “0” used whenresponding negatively. CQI signal is a signal of 5 bits that reports areceiving level.

In a technique of Non-Patent Document 1, ACK/NACK signals and CQIsignals are encoded by using “CAZAC (Constant Amplitude Zero AutoCorrelation)” code. In this conventional technique, the phase shiftamount of CAZAC code used for encoding is varied with regard to each ofthe terminals. It should be noted that the CAZAC code is a code that hasconstant amplitude and no autocorrelation.

However, the above-described conventional technique assigns CAZAC codeof the different phase shift amount to each of the terminals, but has aproblem in which a number of the terminal stations to which the code canbe assigned is small.

[Non-Patent Document 1] 3GPP, R1-062742, NTT DoCoMo et al., “CDM-basedMultiplexing Method of Multiple ACK/NACK and CQI for E-UTRA Uplink”,Oct. 9-13, 2006

DISCLOSURE OF INVENTION

The present invention was conceived in order to solve theabove-described problem and has an object to provide both a wirelessterminal apparatus and wireless base station apparatus that can, in anoperation of encoding the control signals of the upstream linktransmitted from the multiple terminal stations while encoding withregard to each of the terminal stations, increase a number of theterminal stations to which different codes are respectively assigned.

In order to solve the above-described problems, the present inventionprovides, for example, following aspects.

A first aspect is a wireless terminal apparatus which encodes andtransmits a control signal to a wireless base station, including: anencoding information receiving unit receiving encoding information whichis used at the wireless terminal apparatus from the base station; afirst phase-shifting unit which conducts a phase-shifting operation on apredetermined first code based on the encoding information; a codeselection unit which, based on the encoding information, selects asecond code from multiple codes orthogonally crossing each other; anencoding unit which conducts an encoding operation on the control signalby using both the first code on which the phase-shifting operation hasbeen conducted and the second code; and a transmission unit whichtransmits the encoded control signal.

A second aspect is a wireless base station apparatus which communicateswith the above-described wireless terminal apparatus, including: anencoding information transmission unit transmitting the encodinginformation which is respectively different with regard to the wirelessterminal apparatus; a receiving unit the encoded control signal from thewireless terminal apparatus; a second phase-shifting unit which conductsa phase-shifting operation on the first code based on the encodinginformation corresponding to the wireless terminal apparatus; a secondcode selection unit which, based on the encoding informationcorresponding to the wireless terminal apparatus, selects the secondcode from multiple codes orthogonally crossing each other; and adecoding unit which decodes the encoded control signal by using both thefirst code on which the phase-shifting operation has been conducted andthe second code.

A third aspect is the above-described wireless terminal apparatus,wherein the first code has both a constant amplitude and a zeroautocorrelation.

A fourth aspect is a control signal transmission method of a wirelessterminal apparatus including steps of: based on predetermined encodinginformation, conducting a phase-shifting operation on a first code whichhas both a constant amplitude and a zero autocorrelation; based on theencoding information, selecting a second code from multiple codesorthogonally crossing each other; conducting an encoding operation onthe control signal by using both the first code on which thephase-shifting operation has been conducted and the second code; andtransmitting the encoded control signal.

In accordance with the above-described first, second and fourth aspects,in an operation of encoding the control signals of the upstream linktransmitted from the multiple terminal stations while encoding withregard to each of the terminal stations, it is possible to increase anumber of the terminal stations to which different codes arerespectively assigned. In addition, in accordance with theabove-described third aspect, it is possible to use CAZAC that isgenerally known.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a constitution of a terminal station(wireless terminal apparatus) 1 of one embodiment of the presentinvention.

FIG. 2 is a block diagram showing a constitution of a control signalencoding portion 14 shown in FIG. 1.

FIG. 3 is a block diagram showing a constitution of a base station(wireless base station apparatus) 40 of one embodiment of the presentinvention.

FIG. 4 is a drawing for explaining Example 1 in which a first code and asecond code of the present invention are used.

FIG. 5 is a drawing for explaining Example 2 in which a first code and asecond code of the present invention are used.

FIG. 6 is a drawing for explaining Example 3 in which a first code and asecond code of the present invention are used.

DESCRIPTION OF THE REFERENCE SYMBOLS

1 . . . terminal station (wireless terminal apparatus)

11, 41 . . . antenna

12, 42 . . . wireless communication portion

13, 43 . . . control portion

14 . . . control signal encoding portion

15 . . . encoding information receiving portion

21 . . . phase shift portion

22 . . . code generation portion

23, 24 . . . multiplier

40 . . . base station (wireless base station)

44 . . . control signal decoding portion

45 . . . encoding information transmission portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, in reference to the drawings, a preferable embodiment ofthe present invention as an example is explained. It should be notedthat the following embodiments are not limitations on the presentinvention, and for example, it is possible to add, remove or replace theconstitutional elements, and in addition, it is possible to combine theconstitutional elements.

In reference to the drawings, one embodiment of the present invention isexplained below.

FIG. 1 is a block diagram showing a constitution of a terminal station(wireless terminal apparatus) 1 of this embodiment of the presentinvention. The terminal station 1 is a terminal station of a mobilecommunication system and conducts a wireless communication with a basestation explained below. In FIG. 1, the terminal station 1 includes anantenna 11, a wireless communication portion 12, a control portion 13, acontrol signal encoding portion 14 and an encoding information receivingportion 15.

The wireless communication portion 12 receives wireless signals from thebase station via the antenna 11. In addition, the wireless communicationportion 12 transmits wireless signals to the base station via theantenna 11. The control portion 13 transmits/receives control signalsto/from the base station via the wireless communication portion 12. Thecontrol signal encoding portion 14 receives a control signal of anupstream link which is used for a transmission to the base station andconducts an encoding operation on the received control signal. Thecontrol signal encoding portion 14 outputs the control signal afterencoding (encoded control signal) to the wireless communication portion12. The wireless communication portion 12 inputs the encoded controlsignal and transmits the encoded control signal to the base station viathe antenna 11.

The encoding information receiving portion 15 receive encodinginformation from the base station via the wireless communication portion12. The encoding information receiving portion 15 outputs the receivedencoding information to the control signal encoding portion 14. Based onthe encoding information received from the encoding informationreceiving portion 15, the control signal encoding portion 14 obtains acode used for encoding the control signal.

FIG. 2 is a block diagram showing a constitution of the control signalencoding portion 14 shown in FIG. 1. In FIG. 2, the control signalencoding portion 14 includes a phase shift portion 21, a code generationportion 22, and multipliers 23 and 24.

Based on the encoding information received from the encoding informationreceiving portion 15, the phase shift portion 21 conducts a phase shiftoperation on a first code. The phase shift portion 21 outputs the firstcode to the multiplier 23 after the phase shift operation. The encodinginformation output from the encoding information receiving portion 15includes information that indicates amount of a phase shift with regardto the first code. The first code has a constant amplitude and a zeroautocorrelation. It is possible to use, for example, CAZAC code as thefirst code.

The code generation portion 22 generates a second code based on theencoding information input from the encoding information input from theencoding information receiving portion 15. The second code is generatedafter selecting one of multiple codes that are orthogonally crossingeach other. The encoding information received from the encodinginformation receiving portion 15 includes information for determiningthe second code. It is possible to use, for example, Walsh codes as theorthogonally crossing codes.

It should be noted that it is possible to directly include the secondcode in the encoding information received from the encoding informationreceiving portion 15. In other words, the code generation portion 22 canbe a code selection unit that provides a function of selecting thesecond code from the codes which orthogonally cross each other, based onthe encoding information input from the encoding information receivingportion 15.

In the control signal encoding portion 14 shown in FIG. 2, themultiplier 23 which is firstly provided conducts a multiplicationoperation between the control signal input from the control portion 13and the code (the first code after phase shift operation) output fromthe phase shift portion 21. In a following step, the multiplier 24 whichis secondary provided conducts a multiplication operation between asignal output from the multiplier 23 and the code (second code) outputfrom the code generation portion 22. In accordance with such anoperation, the control signal output from the control portion 13 isconverted to the encoded control signal which is encoded by using boththe first code after phase-shifting and the second code. The multiplier24 outputs the encoded control signal to the wireless communicationportion 12.

FIG. 3 is a block diagram showing a constitution of a base station(wireless base station apparatus) 40 of one embodiment of the presentinvention. The base station 40 shown in FIG. 3 is a base station of themobile communication system and conducts a wireless communication to theterminal station 1 shown in FIG. 1. In FIG. 3, the base station 40includes an antenna 41, a wireless communication portion 42, a controlportion 43, a control signal decoding portion 44 and an encodinginformation transmission portion 45.

The wireless communication portion 42 receives wireless signals from theterminal station 1 via the antenna 41. In addition, the wireless portion42 transmits wireless signals to the terminal station via the antenna41. The control portion 43 transmits/receives control signals to/fromthe terminal station 1 via the wireless communication portion 42. Thecontrol signal decoding portion 44 receives the encoded control signaltransmitted from the terminal station 1 via the wireless communicationportion 42 and decodes the encoded control signal after receiving. Thecontrol signal decoding portion 44 outputs the decoded control signal tothe control portion 43.

Via the wireless communication portion 42, the encoding informationtransmission portion 45 transmits the encoding information which isdifferent with regard to each of the terminal stations. In addition, theencoding information transmission portion 45 outputs the encodinginformation corresponding to each of the terminal stations to thecontrol signal decoding portion 44. Based on the encoding informationinput from the encoding information transmission portion 45, the controlsignal decoding portion 44 obtains the code which is used to decode theencoded control signal.

The control signal decoding portion 44 conducts a decoding operationwhich corresponds to the encoding operation by the control signalencoding portion 14 shown in FIG. 2. The control signal decoding portion44 provides a phase shifting portion which conducts a phase shiftingoperation on the first code based on the encoding information which isprovided in correspondence with each of the terminal stations. The phaseshifting operation on the first code in correspondence with each of theterminal stations is conducted. The encoding information correspondingto each of the terminal stations includes information of amount ofphase-shift of the corresponding terminal station. The first code is acode which has both a constant amplitude and a zero autocorrelation, andthe first code is common between the terminal stations.

In addition, based on the encoding information corresponding to each ofthe terminal stations, the control signal decoding portion 44 provides acode selection portion which selects the second code from the codeswhich orthogonally cross each other. With regard to each of the terminalstations, as the second code, one code is selected between the codeswhich orthogonally cross each other. The codes which orthogonally crosseach other and form which the second code is selected are common amongthe terminal stations. The encoding information corresponding to each ofthe terminal stations includes information which specifies the secondcode of the corresponding terminal station.

In addition, the control signal decoding portion 44 provides a decodingportion which decodes the encoded control signal by using both the firstcode after phase-shifting and the second code. Therefore, the encodedcontrol signal transmitted from each of the terminal stations isdecoded. The control signal after decoding is output to the controlportion 43.

In a following explanation, examples of the first code and second codeof this embodiment are shown and explained. Here, CAZAC code is used asthe first code, and Walsh codes are used as “the codes whichorthogonally cross each other” from which the second code is selected.

Example 1

FIG. 4 is a drawing for explaining Example 1 in which the first code andthe second code of this example are used. In the Example 1, a pair ofWalsh codes of two dimensions “(1,1) and (1,−1)” are used. In FIG. 4, acontrol signal area has a 12 bit length, and the encoding operation isconducted on data stored in this 12 bit area. In an example shown inFIG. 4, each of four terminal stations 1 (“UE1”, “UE2”, “UE3” and “UE4”)transmits a control signal of an uplink to the base station 40 which isa single base station.

As shown in FIG. 4, both “UE1” and “UE2” conducts an encoding operationon the control information by using CAZAC codes obtained by aphase-shifting of amount of Δ1. In addition, “UE1” conducts the encodingoperation on the control information by using Walsh code of (1, 1), and“UE2” conducts the encoding operation on the control information byusing Walsh code of (1, −1). In accordance with such a manner, even whenboth of CAZAC codes have the same amount of phase-shifting, it ispossible to conduct encoding operations on the control information ofuplink so as to be orthogonal with regard to each of “UE1” and “UE2”because different Walsh codes are used. Therefore, it is possible toassign a pair of terminal stations to a single phase-shifting amount ofΔ1.

In a similar manner, both “UE3” and “UE4” conducts an encoding operationon the control information by using CAZAC codes obtained by aphase-shifting of amount of Δ2, but different Walsh codes are used.“UE3” uses Walsh code of (1, 1), and “UE4” uses Walsh code of (1, −1).Therefore, it is possible to assign a pair of terminal stations to asingle phase-shifting amount of Δ2.

In accordance with the Example 1, it is possible to assign a pair ofterminal stations to a single phase-shifting amount applied to the CAZACcode. Therefore, compared to a prior art in which CAZAC code with anunique phase-shifting amount is assigned to each of terminal stations,it is possible to increase a number of terminal stations to be doublewhile different codes are respectively assigned to the terminalstations.

Example 2

FIG. 5 is a drawing for explaining Example 2 in which a first code and asecond code are used. In the Example 2, Walsh codes of four dimensions“(1, 1, 1, 1), (1, −1, 1, −1), (1, 1, −1, −1), (1, −1, −1, 1)” are used.In an example shown in FIG. 5, in the similar manner as shown in FIG. 4,an encoding operation is conducted on a control signal area of 12 bits.In the similar manner as shown in FIG. 4, each of four terminal stations1 (“UE1”, “UE2”, “UE3” and “UE4”) transmits a control signal of anuplink to the base station 40 which is a single base station.

As shown in FIG. 5, by using the CZAC codes obtained by phase-shiftingwith a phase-shifting amount of Δ1, all of “UE1”, “UE2”, “UE3” and “UE4”conducts an encryption operation on the control information. It shouldbe noted that each of these terminal stations, by using respectivelydifferent Walsh code, conducts the encryption operation on the controlinformation. “UE1” uses Walsh code of (1, 1, 1, 1), “UE2” uses Walshcode of (1, −1, 1, −1), “UE3” uses Walsh code of (1, 1, −1, −1), and“UE4” uses Walsh code of (1, −1, −1, 1). Therefore, it is possible toassign four terminal stations even though the amount of phase-shiftingis a single value, Δ1.

In accordance with Example 2, it is possible to assign four terminalstations to a single phase-shifting amount applied to the CAZAC code.Therefore, compared .to a prior art in which CAZAC code with an uniquephase-shifting amount is assigned to each of terminal stations, it ispossible to increase a number of terminal stations to be four timeswhile different codes are respectively assigned to the terminalstations.

Example 3

FIG. 6 is a drawing for explaining Example 3 in which a first code and asecond code are used. In the Example 3, in a similar manner as explainedin Example 1, a pair of Walsh codes of two dimensions “(1,1) and (1,−1)”are used. In addition, in a similar manner as explained in Example 1,the encoding operation is conducted on data stored in a control signalarea which has a 12 bit length. It should be noted that the encodingoperation on Walsh codes is conducted only on a predetermined bitposition included in the control signal area of 12 bits. In other words,the encoding operation on Walsh codes is not necessary that is conductedon all bit positions included in the control signal area. In accordancewith Example 3, similarly as described in Example 1, it is possible toassign a pair of terminal stations to a single phase-shifting amountapplied to the CAZAC code. Therefore, compared to a prior art in whichCAZAC code with an unique phase-shifting amount is assigned to each ofterminal stations, it is possible to increase a number of terminalstations to be double while different codes are respectively assigned tothe terminal stations.

As described above, in accordance with this embodiment, compared to aprior art in which CAZAC code with a unique phase-shifting amount isassigned to each of terminal stations, it is possible to increase anumber of terminal stations while different codes are respectivelyassigned to the terminal stations. As a result, it is possible toprovide an advantage in which it is possible to increase a number ofterminal stations that are covered by a single base station.

It should be noted that, in the above-described Examples 1-3, Walshcodes are used as “the codes which orthogonally cross each other” fromwhich the second code is selected. However, Walsh codes are not alimitation for “the codes which orthogonally cross each other”.

For example, it is possible to use orthogonal codes generated fromcomplex numbers as “the codes which orthogonally cross each other”.Following example shows orthogonal codes of a three dimension generatedfrom complex numbers.

(1,1,1)(1, e^(j2π/3), e^(−j2π/3)) (1, e^(j4π/3), e^(−j4π/3))

In addition, it is possible to use orthogonal codes on a rotatingcoordinate system as “the codes which orthogonally cross each other”.Following example is orthogonal codes on a rotating coordinate system oftwo dimensions.

(cosθ,sinθ) (−sinθ,cosθ)

It should be noted that θ is a rotation angle.

When orthogonal codes on a rotating coordinate system are used, byadjusting the rotation angle θ, it is possible to adjust or lowerdetection errors due to differences between reception levels of symbols.

In reference to the drawings, embodiments of the present invention areexplained above. It should be noted that a concrete constitution is notlimited by the above-described embodiments, and it is possible toinclude modifications of the constitution if the modifications is notout of a scope of the present invention.

For example, it is possible to conduct a modulation operation on thecontrol signal. For example, it is possible to apply a modulation ofQPSK (Quadrature Phase Shift Keying, Quadri-Phase Shift Keying) to CQIsignal of 5 bits. In such a case, 2 bits can be transmitted per onesymbol, and hence, it is possible to increase amount of information of acontrol storage area, and it is possible to achieve a highercommunication quality of control signals.

INDUSTRIAL APPLICABILITY

In accordance with the above-described examples, in an operation ofencoding the control signals of the upstream link transmitted from themultiple terminal stations while encoding with regard to each of theterminal stations, it is possible to increase a number of the terminalstations to which different codes are respectively assigned.

1-4. (canceled)
 5. A method of wireless terminal apparatus which encodesand transmits a control signal to a wireless base station apparatus,comprising: by an encoding information receiving portion, receivingencoding information which is used at the wireless terminal apparatusand which is transmitted from the wireless base station apparatus; by anencoding portion, conducting an encoding operation on the control signalby using a predetermined first code, a second code which is anorthogonal code included in or calculated based on the encodinginformation and a phase shift amount based on the encoding information;and by a transmission portion, transmitting the encoded control signal,wherein the transmission portion modulates the control signal using apredetermined modulation method, and the second code includes (1,e^(j4π/3), e^(−j4π/3)).